Telephone lines are frequently brought into central exchanges through large multiple-conductor trunk cables. One trunk cable may include as many as 4,000 conductor pairs. Such a trunk cable may be as much as 3 1/2 inches in diameter. The switching equipment in the exchange is generally designed in units which handle up to 100 separate lines. It has therefore been the practice to connect a plurality of separate cables to a trunk cable, called tip cables, each of which contains 100 conductor pairs. Each tip cable then goes to a switching unit or other piece of equipment. There is, therefore, a need to provide some means of splicing up to 40 tip cables to a single incoming trunk cable. The splice, involving as it does up to 8,000 electrical connections, must be confined to a sealed environment to protect the splice connections from moisture and corrosive contaminants which could have an adverse effect on the terminal connections in the splice. It is therefore desirable to provide a sealed housing for the splice which may be pressurized if necessary to provide an inert environment for the exposed electrical terminal connections of the splice.
It has been the practice in the past to provide a housing in which the cables are brought in through rubber sealing members which are molded with an integral rubber sleeve extending around each opening receiving a cable. The sleeve may be clamped to the cable by a suitable clamping device which extends around the sleeve and squeezes it radially against the outer surface of the cable passing through the sleeve. Such an arrangement has not proved satisfactory for a number of reasons. Because of irregularities in the outer surface of the cable, an effective seal is not always obtained by such a sleeve and clamping arrangement. Where less than the maximum number of cables are brought into the housing, dummy plugs or the like must be made available at the time of installation to insert in the openings through the unused sleeves. Because the clamps are bulky, costly and difficult to install, attempts have been made to provide sleeves with sufficient internal resilience to be self-sealing, but this approach has proved unreliable.